The present invention relates to contact lenses used by ophthalmologists for diagnosis and laser surgery of the eye, and more particularly to an iridotomy and trabeculoplasty goniolaser lens.
Glaucoma is an eye disease that can lead to blindness if not properly treated. Elevated intraocular pressure is frequently an early sign of the disease. Reduction of the intraocular pressure may prevent loss of vision. The goniolaser lens may be designed to focus the laser light to treat two specific types of glaucoma.
Angle-closure glaucoma: In angle-closure glaucoma the intraocular fluids (aqueous humor) must pass through the pupil from behind the iris (posterior chamber) to a position in from of the iris (anterior chamber). The aqueous humor then escapes from the eye through microscopic channels located at the angle of the anterior chamber between the peripheral iris and cornea. In angle-closure glaucoma there occurs a block at the pupil so that the aqueous humor cannot pass from the posterior to the anterior chamber and the eye pressure becomes very elevated.
One method developed for relief of intraocular pressure caused by angle-closure glaucoma is to perform an iridotomy using laser ablation surgery. This surgical procedure is accomplished by positioning an appropriately configured contact lens on the cornea of an eye and delivering laser energy to the iris. The laser energy is focused on the peripheral iris to generate an opening through the iris. Intraocular fluid (aqueous humor) can then bypass the blocked pupil and move through the newly created iris opening from the posterior to the anterior chamber. This allows the aqueous humor to reach the outflow channels in the anterior chamber angle and relieve the pressure and symptoms of closed angle glaucoma.
Open-angle glaucoma: Open-angle glaucoma is caused by an abnormality in the microscopic channels, trabecular meshwork, that are located in the angle of the anterior chamber. Eyedrop medications may help the aqueous humor to pass through the meshwork, but not in all cases.
Another method for relieving the symptoms of open-angle glaucoma is to perform trabeculoplasty using laser ablation surgery. This procedure is accomplished by delivering laser energy to the trabecular meshwork to allow better passage of the aqueous humor through it. One theory suggests that the laser alters the intracellular and intercellular structures in the trabecular meshwork and allows the fluids to pass through with less obstruction.
Prior contact lenses employed for these purposes work efficiently for the application of laser energy to the eye. However, viewing the trabecular meshwork before and after an iridotomy procedure has necessitated removal of the laser lens and substitution of another viewing lens. While attempts have been made at combining a laser delivery lens and a viewing lens, the attempted combinations have not been successful for a variety of reasons. The major reason for lack of success has been the necessity to completely refocus the binocular microscope through which the surgeon is manipulating the laser energy and through which the surgeon views the trabecular meshwork.
During an iridotomy procedure, it is desirable to view the trabecular meshwork immediately after the delivery of laser energy to determine the efficacy of the procedure. If the aperture through the iris has been successfully completed, fluid pressure in the posterior chamber will be relieved and will allow the iris to flatten to its natural state rather than the anteriorly bowed configuration that occurs in the presence of excessive intraocular pressure in the posterior chamber. When laser iridotomy has been mechanically successful, the anterior chamber angle will open, as observed through the gonioscopy portion of the lens. However, if it is observed that the angle failed to open, then additional application of laser energy may be required. Thus, if the anterior chamber angle and trabecular meshwork could be viewed immediately after the initial delivery of laser energy through the same contact lens, an additional application of laser energy could be applied to the same or another location without removing the laser delivery lens, without substituting the viewing lens and without once again repositioning the laser delivery lens.
In accordance with the present invention, an iridotomy goniolaser lens is provided through which laser energy can be delivered to the eye and through which the treated area can be observed. In a currently preferred embodiment, the lens comprises four elements: a contact lens, a planar mirror, a first button lens, and a second button lens. The contact lens has an optical axis, a concave posterior contact surface, and an anterior planar surface. The contact lens element has an angled surface offset from its optical axis. The angled surface is planar and extends laterally and anteriorly from a location radially offset from the optical axis of the contact lens element and adjacent to the concave contact lens surface but anterior thereof. The surface forms an internally reflective planar mirror. The first button lens has a planar posterior surface and a convex anterior surface. The planar surface of the first button lens is in optical contact with the planar surface of the contact lens element and is offset from the optical axis of the contact lens element in a direction opposite from the offset of the angled surface. The magnification, curvature, and location of the first button lens is chosen to provide a virtual image in a first image plane of a predetermined location on the iris of a patient when the contact lens surface of the contact lens element is in optical contact with the cornea of the eye of the patient. The second button lens has a planar posterior surface and a convex anterior surface. The planar surface of the second button lens is in optical contact with the planar surface of the contact lens element. The second button lens is offset from the optical axis of the contact lens in the direction of the offset of the angled mirror surface and is positioned over the angled mirror surface. The magnification, curvature, and location of the second button lens is chosen to provide a virtual image in a second image plane of the trabecular meshwork of the eye of the patient when the surface of the contact lens element is in optical contact with the cornea of the eye of the patient. The magnification, curvature, and location of the first and second button lens are preferably chosen such that an optical microscope can be focused on the first and second image planes with little or no focus adjustment, thus allowing delivery of laser energy to the iris and viewing of the trabecular meshwork through the same lens.
The same lens can be employed for trabeculoplasty. For this procedure, laser energy is directed toward the angled mirror surface and reflected to the trabecular meshwork. The results of the trabeculoplasty can be viewed along the same optical path.